1. Field of the Invention
The present invention relates to an automatic image quality adjusting device for a magnetic signal recording and reproducing apparatus and, more particularly, to an automatic image quality adjusting device which automatically varies the frequency characteristics in a reproduction process of image signals in accordance with the magnitude of an envelope of each video signal output from a reproduction head so that optimal image quality can automatically be achieved.
2. Description of the Prior Art
In order to vary a quality of a reproduced image, conventionally, an image quality adjusting device is provided for any of the magnetic signal recording and reproducing apparatuses to allow the user to optionally vary the image quality as the user desire's.
A typical example of a conventional image quality adjusting device is shown in FIG. 6. A video signal reproduced from a video tape by a video head 1 is initially amplified by a pre-amplifier 2, and then, the amplified video signals are divided into a frequency-modulated luminance signal Y and a color signal C of a low-level converted frequency. The frequency-modulated luminance signal Y is applied to an RF amplifier 3 which compensates the frequency of signal Y to produce a frequency compensated luminance signal Yc'. Then the frequency compensated luminance signal Yc' is demodulated and a demodulated luminance signal Yd' is produced by a demodulator 4. The demodulated luminance signal Yd' is then amplified by an amplifier 5 which then produces an amplified luminance signal Ya'. The amplified luminance signal Ya', thus obtained, is delivered to a television monitor 6, at which the user adjusts the image quality by manually operating a resistance controller R1 coupled to the amplifier 5 so that the frequency characteristic of the amplifier 5 is manually varied. Since video tapes from which the video signals are reproduced have different characteristics depending on the type of the tape used or the number of times the tape has been replayed, the luminance signal Ya' varies with respect to the tape. Thus, it is necessary for the user to adjust the luminance when there is a luminance change which may occur when the tape is changed, or within the same tape but at different portions.